Computer Expansion Boxes of the 1980s and 90s

A Brief History

Why upgrade a personal computer or game console internally—when instead you can externally attach ungainly boxes! And as a bonus, use up more desk space!

No mere peripherals, these extenders were meant to change your whole computing / gaming experience—whether they succeeded is another question.


Nicknamed the Blue Whale, the “Keyboard Component” was a major promised upgrade for the Mattel Intellivision console. Intellivision started back in 1977, with the first games programmed by Caltech summer interns.

The Keyboard Component was far beyond a keyboard and had some impressive features:

contained 16K of shared dynamic RAM and its own 6502 processor to handle I/O functions. Special programs were available on cassettes. The built-in tape deck featured a sophisticated block-addressable cassette interface; an audio track could be synchronized with a program and its graphics. With the provided microphone, parts of the audio track could be re-recorded and played back under program control. A cartridge port allowed standard Intellivision games to be played without removing the Master Component, and a printer port allowed output to a 40-column thermal printer.

Blue Sky Rangers

People were still waiting for the Keyboard Component in 1981-1982 but it never reached wide distribution.

The delays actually brought the attention of the FTC and eventually several lawsuits. In 1982 Mattel released a less powerful computer module called the “Entertainment Computer System” which had been “quietly developed by a different division.”

Though approximately 4,000 Keyboard Components were manufactured, it is not clear how many of them were sold and they are rare. Many of the units were dismantled for parts.



The Atari VCS—later called the Atari 2600—kind of created the whole home game console market starting in 1977 and led it in the early 80s up until the Video Game Crash of 1983.

The Spectravideo CompuMate extension, released in 1983, aimed to turn the Atari into something resembling a PC.

Unlike most devices mentioned here, this one didn’t add a processor. But it did physically fit a keyboard right on top of the console, provide a way to save / load programs, bring 2K of RAM, add a BASIC programming interpreter, and a music composing / playing program and a paint program.

Source: Avon Fox,

The keyboard plugged into the 2600’s cartridge port as well as both joystick ports and sat impressively on the 2600’s main flat surface shouting, ‘look at me, I’m a computer now!’


Imagine you’re reading Byte Magazine in April 1985, and you come across this first page of a three-page ad:

Wow, that looks like the Apple ad font. Is this some new Apple tech? And then you turn the page to find:

Huh? I suppose at that point in history it might have been very useful to be able to run DOS software on a Mac just as it was later with Microsoft office applications on Macs.

From a company called Dayna, the MacCharlie—the “Charlie” referencing IBM’s Charlie Chaplin ads—was a hardware + software solution to allow text mode DOS access in MacOS. And you could transfer files between the two systems, print “MacCharlie documents” on your Apple printer and do networking through the PC side.

Source: Deskthority (public domain)

Here’s a rear view:

The MacCharlie box is essentially an IBM-compatible PC with an 8088 processor and one or two 5¼” floppy drives. Despite that it “clips” onto the side of the Mac, and even has a thing to clip around the keyboard to provide more keys, there was no direct bus connection happening—the Mac and PC were connected with an RS-232 serial cable. Probably best they didn’t try to transfer video.

MacCharlie was taken by many to be an April Fools joke

Daniel Knight, Low End Mac

Text mode could be useful but certainly wasn’t the wonderful world the ad seemed to imply especially since PCs were doing interesting graphics (and in color!) back then including Microsoft Flight Simulator 2.0.

However, as soon as I began testing software, I ran into a major snag. MacCharlie will accept only software that does not use graphics. I didn’t expect to see color on the Macintish monochrome monitor, but a Mac without graphics? That’s like a hamburger without a bun and ketchup.

Erik Sandberg-Diment, NY Times, Sept. 24, 1985


In 1986, Commodore released the Amiga Sidecar.

Source: Wikimedia (CC BY-SA 3.0)

The Sidecar, like MacCharlie, was an 8088 PC in a box but this symbiosis could also do graphics and sound—because Amiga had a proper expansion port unlike Macs (the port is on the right side of the Amiga).

And it could run Microsoft Flight Simulator. (The native Amiga version of Flight Simulator was not finished until late 1986.)

Apparently you could also configure it to run a second monitor off the PC side:

It used a lot of desk space, and quickly Amiga reduced it to an internal expansion card called Bridgeboard for Amiga 2000+ models so you wouldn’t need a whole ass box on the side.


Sega’s shiny black plastic encased machinery was definitely more sexy than the early game consoles as well as the parade of beige personal computers and even the mostly-gray Nintendos of the era.

First up is the Sega CD (1991) which mated with the first two generations of Genesis (aka Mega Drive).

Source: Sega Retro (CC BY 4.0)

You can see the bus connector is on the right side. Sega was wise in retaining the same position and type of expansion port so most or all combinations of old and new models could be either stacked…

Source: Sega Retro (CC BY 4.0)

…or connected side-by-side.

Source: Sega Retro (CC BY 4.0)

Sega CD not only enabled CDs, and more storage capability through CD-ROM games, but also included another processor. Graphics were apparently mostly unchanged however, and annoyingly it required an additional wall wart.

Next is the Sega 32X (1994) which tried to vastly improve the graphics but was not the big hit it could have been. This plugged in to the cartridge slot on the top like a slick blobby remora.

The 32X provided a secondary cartridge slot on the top that could accept 32X games or act as a pass-through for standard Genesis games.

Source: Sega Retro (CC BY 4.0)

Unfortunately it required yet another power supply. And it looks like you had to connect the 32X directly to the TV.

The 32X could be combined with the CD, and there were something like six games that took advantage of both.

Source: Sega Retro (CC BY 4.0)

Sega also released the game Sonic & Knuckles with a built-in pass-through connector so you could plug in other Sonic games to gain Knuckles as a character in those. Naturally some people have stacked all of this together. Here’s one with all that and a Game Genie thrown in:

Final Remarks

The Sega extensions must have been the most rewarding to physically connect. I’m extrapolating from my experience of having a Genesis and Sonic & Knuckles as a kid.

Directly snapping / sliding electronic devices together without cords or wireless-over-the-air seems to have all but disappeared.

But in another way that kind of interface evolved for robotics. When I worked at iRobot’s defense division (now part of Teledyne FLIR) they had many robot arm joints that used slip rings so that arm segments could easily be removed / replaced without ever seeing a wire or needing special tools.

Perhaps the convenience and haptic joy of cordless-direct-contact interfaces is a small part of the popularity of the Nintendo Switch, which is presently the third bestselling game console of all time.

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